Salmon population trend summaries

Salmon population trend summaries

This page contains summaries of abundance trends for populations within salmonid Evolutionarily Significant Units (ESUs) listed under the Endangered Species Act in the Pacific Northwest. These summaries were prepared to aid in reporting under the Government Performance Results Act, and are intended for overview purposes only. Please see the viability reports developed by the Technical Recovery Teams for more detailed information regarding the status of listed ESUs. The data used for calculating trends are available at the NWFSC’s Salmon Population Summary database on the Scientific Data and Tools page.

Where possible, trend information was compiled from the most recently available spawning abundance estimates obtained from state or tribal biologists, using the methodologies for reporting spawning abundance developed by the Technical Recovery Teams. For some ESUs, an entire ESU abundance count was available in the form of a dam count, and in some cases these counts were used when population specific data were unavailable.

The trend for each population within an ESU or DPS for which data were available was calculated using the approach described by Good et al. (2005). Briefly, the trend was calculated as the slope of the linear regression of log transformed natural origin spawning abundance over the last 10 years of available data. Each population trend was classified as “no trend” if the slope of the trend was not significantly (p < 0.05) different from zero; “increasing” if the trend was significantly greater than zero; and “decreasing” if the trend was significantly less than zero. The trend for the ESU or DPS was inferred from the population level trends as follows:  if at 75% or more of the population level trends were either significantly increasing or decreasing, then the ESU or DPS trends was reported as that category; otherwise the ESU or DPS trend was reported as either “mixed” or “stable” as seemed most appropriate.

Salish Sea Domain

Willamette River and Lower Columbia River Domain

Interior Columbia River Domain

Oregon Coast Domain



For assistance with these documents, contact Mike Ford.




last modified 05/16/2013